1. Field of the Invention
The present invention relates to a control device that controls warm-up of a machine.
2. Description of the Related Art
Warm-up is carried out in machines that need to operate in high accuracy, in order to stabilize the operational accuracy or operational results of the machines. The warm-up is intended to prevent the operational accuracy of a machine from being affected by stretched and contracted drive elements of the machine caused by temperature change during machine operation. In general, the drive elements of the machine are expanded as the temperature of the drive elements of the machine rises, which generates a difference between behavior (e.g., operation paths) of the drive elements of the machine with relatively low temperature immediately after starting the operation and behavior of the drive elements of the machine that has been sufficiently warmed up. As a result, stable operational accuracy of the machine is not assured from starting the operation until the machine is sufficiently warmed up.
As a general rule, a warm-up is preferably completed before performing an intended regular operation (machining, when the machine is a machine tool). However, there is a possibility that performing the warm-up may result in a reduction of the actual operation time, thereby lowering product efficiency. In other cases, when an operator carries out the warm-up outside working hours, labor costs increase accordingly.
JP-A-2013-163255 discloses a warm-up control device that is configured to automatically perform a warm-up even when a machine tool has been left alone after a warm-up stopped. Further, the control device disclosed in JP-A-2013-163255 is configured to determine whether or not to perform the warm-up again based on a thermal displacement amount that changes over time.
JP-A-2010-105101 discloses an electric discharge machining device that is configured to allow an operator to immediately start a machining task at task start time. In the electric discharge machining device described in JP-A-2010-105101, unnecessary power consumption is intentionally reduced by switching between a normal mode and a power-saving mode. The switching between the modes is performed at a preset time.
However, while the preparation process of a machine may be automatically performed at predetermined start time, the electric discharge machining device described in JP-A-2010-105101 needs a device that circulates machining liquid outside the machine in order to prevent thermal displacement of the constituent portions, which increases costs for the machine. In addition, configuration for circulating the machining liquid through the drive elements (e.g., ball screws and the like) of the machine as a control object is complicated and, thus, such configuration is difficult to realize. Therefore, there is a need for a control device with a low-cost and simple configuration, which can automatically and efficiently perform a warm-up without need of additional devices.